The present invention relates to a plasma processing apparatus and a plasma processing method and more particularly to a plasma processing apparatus and a plasma processing method of plasma-processing a sample while applying time-modulated high-frequency bias to the sample in the etching processing of the sample using the time-modulated plasma.
In the fabrication process of semiconductor devices, the dry-etching process using plasma is applied generally. Plasma processing apparatuses of various methods of performing dry-etching are employed.
In recent years, reduction in the processing size of related-art semiconductor devices made of silicon material basically to attain high performance and low cost of the semiconductor devices is reaching physical limitation. The time that technical nodes of semiconductor devices represented by logic semiconductor device circuits, DRAM's (Dynamic Random Access Memories) and flash memories are 20 to 10 nm is encountered and in order to achieve high performance of the devices using the technical nodes, new material and device structure which are not adopted in the manufacturing process of semiconductor devices used so far must be adopted. Actually, new material except silicon and new structure such as solid transistor are adopted as new measures for miniaturization of logic LSI's and semiconductor memories.
A demand required for a plasma processing apparatus used in the etching process upon manufacturing of semiconductor devices is also severe increasingly with great evolution of the material and the structure of semiconductor devices. Particularly, great improvement in miniaturization of processing size, etching selectivity and high-accuracy control of etch profile is demanded. The miniaturization of processing size is required to be maintained to be uniform in case where the technical node is shifted from 20-nm generation to 10-nm generation, the processing size that must be controlled in the etching process is scattered within the range of several nm to several angstroms and the scattering accuracy of the miniaturization processing is 12 to 18 inches in the diameter of a wafer.
Further, it is requested not only to control etching chemical reaction using related-art silicon material as basis but also to process new material such as III-V family, graphene and carbon nanotube with sufficient etching selectivity. In order to cope with the new material and the new structure represented by the high aspect ratio for realizing the solid transistor, it is indispensable not only to produce etching reaction considering only plasma density and incident energy of ions as a related-art plasma processing apparatus but also to produce etching reaction considering control of reactive radical species, control of electron temperature, control of ion flux, ratio of neutron flux and ion flux, control of dissociation degree and the like.
Actually, in order to complement difficulty in processing control of etching profile due to complicated multi-layer structure and solid structure, an attempt has been made to control the ion generation amount and the radical generation amount optimum to etching processing of laminated layers and structures.
As one method thereof, there is a method of generating plasma intermittently. For example, JP-A-8-250479 discloses that the etching processing process of the dry etching includes a first period A containing the elementary process where reactive species is absorbed to the surface mainly, a second period B containing the elementary process where the surface is irradiated with particles accelerated so as to promote reaction of absorption reactive species and material and a third period C containing the elementary process where reactive products are detached from the surface to be discharged and the processing process including the first to third periods A, B and C is periodically performed on a cycle of 1 msec to 1 sec.
Further, as a method of controlling the etching profile using pulsed plasma, U.S. Pat. No. 7,785,486 discloses that pulse frequency of the pulsed plasma is increased to an odd multiple of frequency of modulation pulse train for high-frequency bias.
These related techniques are concerned with the technique of generating plasma intermittently in order to control the etching profile with high accuracy. In these related techniques, energy for generating plasma is modulated regularly in a plasma generation apparatus which generates plasma in a plasma processing apparatus. For example, energy is turned on and off or energy is modulated to be applied to plasma. When energy for generating plasma is high level, generation of ions is increased as compared with generation of radical whereas when energy for generating plasma is low level, generation of radical is increased as compared with generation of ions.
Further, ionic species and radical species unnecessary to control the etching selectivity and the etching profile are controlled by turning on and off energy or modulating energy. In this manner, the ion generation amount and the radical generation amount are controlled with high accuracy to improve the processing accuracy.